@Rolfy - I use the shader heavily in all of my games and know its requirements and tweaks very well.
@ Willow - at least I got now a beautiful entity icon. Thank you very much.
@ RelMayer - You gave me the clue I needed, with your setup.ini.
I found the reason and the solution.
in my entityfolder I saw the Quality Change.txt file being updated on every text run. I took a look into it and saw on error there. this lead me to the assumption it has to do with the application of lightmaps onto the objects.
Then i rechecked my setup.ini against the one posted by Relmayer
And yeah, I had (for memory reasons)
lightmaptexsize=256
in there.
After I changed to
lightmaptexsize=512
it worked.
Unfortunately, now the memcap is reached even sooner. Will have to sacrify a goat to some dark gods in order to ensure that 1.20 will bring relieve.
Edit: Everyone who posted here can use the model.